Identification animal ear tags for cattle, hogs, sheep and the like are in widespread use. The most popular forms of these tags comprise two components formed of plastic or other resilient material, the male component having a pointed pin, spike or rivet of hard plastic material which is adapted to be forced through an animal ear and the female component which can be urged over the pointed end of the rivet to retain the male component in position on the ear. The means of identification, i.e., the tag itself, can be attached to or integrally formed with either or both components of the two-component tag. U.S. Pat. Nos. 4,544,547, 4,581,834, and 4,694,781; U.K. Pat. GB 2 062 552: and PCT patent publication WO 82/01639 describe exemplary two-component tags.
As ear identification tags for animals are increasingly used, various techniques also have been devised for using such tags to topically release agents such as insecticides, insect repellents or animal repellents, either through separately applied tags or by adding a carrier of some type to the identification ear tag. However, these all have certain problems or drawbacks in addition to being for topical rather than transdermal delivery of agent. Those ear tags where the tag itself is made of a material impregnated with an insecticide, such as disclosed in U.S. Pat. Nos. 4,184,453 and 4,265,876 for example, pose the problem that within a relatively short period of time the insecticide is used up. Where the tags have been adapted to include replenishable insecticide devices (examples of which are disclosed in U.S. Pat. Nos. 3,949,708, 4,425,874, 4,562,794, 4,694,781 and 4,697,549), the tags themselves are of special construction to accommodate the the different insecticide dispensers. With insecticide carriers which are wrapped around a portion of the tag to fasten upon themselves, removal and installation of the carriers is cumbersome. Examples of such carriers are described in U.S. Pat. Nos. 4,366,777 and 4,495,898. Additionally, all are for topical rather than transdermal delivery of an active agent.
Transdermal drug delivery in veterinary applications is discussed by Pitman and Rostas in Journal of Pharmaceutical Sciences, 70(11):1181-1193 (1981), and 71(4):427-430 (1982). A few techniques and devices are known for administering medicaments through the skin for veterinary use. One example of such a technique is described in U.S. Pat. No. 4,026,290, which suggests attachment of a device to the ears or tail of an animal for applying a drug. Another example is described in EP application 376,143, which describes a device which is wrapped completely around the ear.
Transdermal drug delivery devices for placement by adhesive means onto the skin are well-known for use with humans. Examples of such devices are described in U.S. Pat. Nos. 3,598,122, 3,598,123, 4,379,454, 4,286,592, 4,314,557 and 4,568,343, for example, all of which are incorporated herein by reference. However, such devices are not useful for animals. Retention is not reliable because of exposure to weather or of animal behavior such as grooming. Also, locations free of hair growth to allow the use of aggressive adhesive are rare. Moreover, any dramatic change in animal handling practices required of livestockmen would be met with resistance.
Accordingly, it is desirable to provide an active agent transdermal delivery device which is practical and simple to use, can be manufactured economically, may be used in conjunction with a standard unmodified ear identification tag and which is easy to apply and easy to remove and is readily removable without requiring removal of the identification tag. It is also desirable to provide a device for transdermal delivery without altering animal handling practices or increasing cost.